1. Field of the Invention
The present invention relates to an image forming apparatus such as a copy machine, a printer, or a facsimile machine which employs an electrophotographic method or an electrographic recording method.
2. Description of the Related Art
In recent years, image forming apparatuses are arranged, during image formation, to change image forming speed according to, for example, the type of recording material or the image to be formed. A high-quality image can be formed by setting the speed to a suitable image forming speed. However, the generation of a speed difference between a photosensitive drum and an intermediate transfer member, when switching the image forming speed, leads to a deterioration in the formed image caused by abrasion of the members.
Japanese Patent Application Laid-Open No. 2003-207981, for example, discusses a technique in which the speed of a photosensitive drum and the speed of an intermediate transfer member are detected using an encoder to reduce the speed difference between the photosensitive drum and the intermediate transfer member such that it falls within a predetermined range. Thereby, image deterioration caused by abrasion of the photosensitive drum and the intermediate transfer member can be reduced.
However, even when control is performed as discussed in Japanese Patent Application Laid-Open No. 2003-207981, it is difficult to completely eliminate a circumferential speed difference between the photosensitive drum and the intermediate transfer member, which may cause a slight deterioration due to the abrasion of the photosensitive drum or the intermediate transfer member.
In view of the above, a control method can be also considered, which stops a photosensitive drum and an intermediate transfer member and then drives the photosensitive drum and the intermediate transfer member again at a new desired speed, to suppress the generation of a circumferential speed difference when changing an image forming speed. However, there is an issue that when such control is performed, it takes increased time to change the image forming speed.